Electric-current transmission



Patente'd Apr. 10, 1928.

UNITED STATES PATENT OFFICE- WILLIAM S. GORTON, OF'LONDON, ENGLAND, ASSIGNOR T0 WESTERN ELECTRIC COM- IPANY, INCORPORATED, 013 NEW YORK, N. Y., A CORPORATION OF NEW YORK.

ELECTRIC-CURRENT TRANSMISSION.

Application filed January 26, 1923. Serial No. 615,164.

This invention relates to the transmission of electric currents, and aims especially to provide improvements in the two-way transmission of such currents, for instance in the two-way repeating of telephonic currents.

In the particular embodiments of the invention shown in the drawing, this object is accomplished by employing two oppositely pointed oneway electron tube repeaters, an

electron tube network individual to each repeater and associated with the input and with the output of the repeater, and a polarized electron tube relay fed from the networks and controlling the potentials of the grids of the repeaters and of certain of the tubes of the networks. Reversal of the pointing of the repeater system occurs only upon the approach toward the repeater system, from the direction toward which it is pointed, of power sufiicient to cause operation of the polarized electron tube relay through the medium of an electron tube comprised in one of the networks and having its grid and filament connected across the line section from which the energy is approaching the repeating system.

This operation of the relay controls the grid potentials of the repeaters, to cause the repeater which was last operative to be inoperative and to cause the other repeater to be operative, and also controls the grid potentials of certain of the tubes of the networks in such a manner that although the current from the output of the operative repeater tends to cause the input voltage of the relay to be such as to again reverse the relay, this tendency is overcome by the tendcncy of the current incoming into the repeater system to cause the input voltage of the relay to be such as to maintain the new relay setting. When the transmission in the line reverses so as to approach the repeating system from the direction toward which the repeating system is pointed, the last mentioned tendency is absent, and the current incoming into the repeater system acts, through a tube which iscomprised in the network associated with the repeater last operative and which has its grid and filament connected across the line section from which energy is approaching, to cause the sign of the input voltage of the relay to reverse so that the relay reverses the pointing of the repeating system in a manner similar to that described above.

Thus, the invention -provides a control effect of a character dependent upon the direction of the transmission in a hne b balancing energy of the transmission at t e in-- put side of a unilateral element, such as an amplifier, in the line against energy of transmission at the output side of the unilateral element, and utilizes the control. effect to control the transmitting efiiciency of a transmission pathcomprising the amplifier. Moreover, the invention provides for twoway repeating without necessitating balancing the impedance of the lines connected to the repeater system to avoid singing of the repeater system due to local circulation of power between the repeater elements, and without involving changes in the continuity or arrangement of the transmission circuits employed, and makes such provision with out causing undue distortion of the currents to be repeated and in such manner that when the repeater system has been put inv condition to repeat in one direction it remains in such condition until power suflicient to cause reversal of the pointing of the repeater sys tem approaches the repeater system from that direction.

Fig. 1 of the drawing is a'circuit diagram of one embodiment of the invention; and Fig. 2 is a diagram of the preferred embodiment, employing push-pull repeaters.

R and- R are repeaters for transmitting energy from line Vito line E and from line E to line WV, respectively, the repeater R being coupled to line W by transtormer 1 and to line E by transformer 2, and the repeater R being coupled to lines E and W by transformers 4 and 6. respectively. Associated with the input of repeater R is an amplifier 3. and associated with the output of the repeater R is an amplifier 5. Similarly,

there are associated with the input and with ment when energy is flowing through a repeater the direct current in the resistances 10 or 11 common to the plate circuits of the two amplifiers flowsin a certain direction. \Vhen energy flows into the output of a reeater the. direct current in the resistance ]HSt referred to is in the opposite direction.

The electro-motive forces developed by thedirect currents flowing in the resistances 10 and 11 are'applied' to the input of a polarized vacuum tube relay 12. This relay comprises two three-electrode electron tubes 13 and 14 connected together so that-the grid potential of tube 13 is controlled by the plate current of tube 14, and the grid potential of tube 14- is controlled by the plate current of tube 13 in such a manner that an increase of current in the tube 13 makes the grid of the tube 14- more negative than before, thus decreasing the current in the tube 14, whichcauses an increase of potential on the grid of the tube 13 and thus tends to further increase the current in the tube 13. In a similar manner an increase of current in the tube 14 results in a decrease of current in the tube 13 and consequent tendency to still further increase the current in the tube 14. The device is thus one which is in an unstable condition when the current in the two tubes is the same or nearly the same and is stable only when the-current in one tube has increased to a maximum and the current in the other one decreased to a minimum or to zero.

The tubes 13 and 14 may have a high vacuum or may contain a certain amount of gas contributing to their action. The grid, filament, and plate of tube 13 are designated 15,

I to plate 17 makes grid 18 less negative, and

if the current to plate 17. becomes zero grid 7 18 assumes the same potential as filament 19 since the current in resistance 23 is in this case zero. In the same manner, the current to plate 20is supplied through a resistance 24 to one point 25 of which the grid 15 is connected through a circuit comprising elements as, 27, 2s, 11, 29, 30, 31, 32, 10, 33 and 34. This circuit is also the circuit for applying to the input electrodes 15, 16 of relay 12, the electromotive forces developed as described above by the direct currents flowing in the resistances 10 and 11. Connected with the output of the relay through leads 26 and 35, are two tubes 36 and 37 which control the amplification of the repeaters R and R and of the amplifiers 3 and 7 associated with their inputs, as described hereinafter. The operation of the relay 12 will now be described somewhat more in detail.

In the normal condition, without any voltage being applied across the leads 26 and 34, the current in one relay tube is much greater than that in the other, and if properly adjusted the current in the latter will be zero. Let us suppose that a current I flows to the plate 17 and that no current is flowing to the plate 20, the negative potential of grid 18 being'sufficient to reduce the current in the second tube to zero. Now, if volt- .age be applied across the leads 26 and 34 ingly be decreased, grid 18 will be made more nearly positive, a current will flow to the plate 20 which will cause a fall of po; tential in resistance 24 making grid 15 still more negative, and as a result of this action, if the voltage assumed to be applied to leads 26 and 34 is of sufiicient magnitude, the current to plate 20 will exceed that to plate 17, and will cause the current in plate 17 to drop to zero, and a new condition of stability will be established in which the current- I will flow to plate 20 and cause the relay 12 to deliver an electromotive force to tubes 36 and 37, but no current will flow to plate 17. This condition will persist until a' sufficient. positive potential is given to grid 15 by applying voltage in the proper direction to theleads 26 and 34. This system thus operates similarly to an ordinary polarized electromagnetic relay and may for convenience be called a polarized thermionic relay. It is stable in either one of two conditions and unstable under intermediate conditions, and requires a voltage of proper direction and of definite value to throw it from one condition of stability to the other.

The operation of the repeating system will now be described. Consider the repeater to be operative for energy flowing east. In that condition the tube 13 will have a maximum plate current, the tube 14 zero plate current, and the repeater control tubes 36 and 37,

memes maximum plate currents, thus making R operative and R inoperative since a positive voltage due to drop in resistance 38 in the plate circuit of tube 36 is introduced between the filament and the grid of R by means of leads 39 and 40, whereas a negative volt-age 'due to drop in resistance 41 in the plate circuit of tube 37 is introduced between the filament and the grid of R by means oij leads 42 and- 4:3. The C battery 50 of repeater R applies to the grid of this repeater a negative potential of such value as to render this repeater inoperative when the potential received from the drop across resistance 38 is zero; but when the repeater control tubes 36 and 37 have their maximum plate'currents the potential received by the grid of this repeater due to voltage drop in resistance 38, is sufficient to cause the repeater R to operate at such a point, on its plate current-grid potential characteristic as to give distortionless amplification, in the manner Well known in the art. WVhen the drop across resistance 41 is zero, the C battery 51 of repeater R applies to .the grid of this repeater a negative" potential of such value as to cause this repeater to operate at such a point on its plate current-grid potential characteristic as to give distortionless amplification; but when the repeater control tubes 36 and 37 have their maximum plate currents the potential received by the grid of this repeater due to voltage drop in resistance 41 is sufiicient to render this repeater inoperative. As long as energy continues to flow east the efiect of the amplifier 9 and of the amplifiers 3 and 5, is to maintain R operative and R inoperative. The amplified output of R enters the input of R but does nothing there as R and its input amplifier 7 are inoperative.

When energy flows West it enters the output of R and the input of R The only operative amplifier which it meets is amplifier 5 connected to the output of R The operation of this amplifier causes a reversal of the potential applied to the grid of the tube 13 of the relay 12 and the relay will reverse almost instantly when this potential exceeds a certain definite amount. The reversal of the relay makes R inoperative and R operative, thus transmitting energy through the repeater to the west.

The grid potentials of R and R should be so arranged that there is no value of-the plate currents of the control tubes 36 and 37 for which both repeaters are operative, so that there will be no time during which both repeaters are operative, and no consequent.

singing. If singing should occur due to any cause it would probably be of very high frequency and so could be easily stopped by the use of a small amount of reactance which would have very little effect upon the voice the small erative, as shown in Fig. 1, by variation of the plate currents sends out large impulses of energy upon the lines. This can be obviated by making the repeaters of the pushpull type, as shown at R and R' in Fig. 2 which is otherwise like Fig. 1. The use of the push-pull. repeaters to avoid the creation of the noise currents is the invention of Beatty, and is claimed in his Patent, No. 1,470,954, issued 1 October 16, 1923, entitled Repeating methods and systerns, assigned to the assignee of this application.

This repeater requiresthe application of a certain finite amount of energy before it will reverse itself, but once the energy rises to the proper value, the repeater reverses itself quickly enough to insure that the last portion of the first syllable approaching the repeater from its output side is small, and that the listener has ample opportunity to easily break in on the talker when short pauses occur in the transmission from the talker.

The function of condenser 60, 61, 62 and 63, is to smooth out the current pulses delivered by tubes 3, 4, 7 and 9, respectively, to the resistances" 10 and 11. In other words, these condensers cause the fluctuations of voltage across these resistances to be slowparts ofresistances 10 and 11 across which they are respectively connected.

The purpose of resistance 31 is to prevent circulating currents which might flow in the following fashion; consider resistance 38. Starting out from the upper point of that part of the resistance which applies potential to the grids of one of the repeater elements by traversing elements 38, 33, 10, 32, 31, 30, 29, 11, 28 and 27, we arrive at the lower end of the above mentioned portion of resistance 38. Thus, resistances 38, 10 and 11 are inter-connected and any two of these resistances will act as a shunt upon the remaining one. The currents flowing as a.

consequence of thisinterconnection are such as to interfere with the proper actionmf the system. To prevent the circulation of currents through these inter-connections resistance 31 is inserted in the circuit. 31should have a value which is high compared with those of the otherthree resistances mentioned. As a consequence the circulating currents are reduced to negligible Resistance amounts and at thesame time the proper functioning of the repeater is not interfered with as connection 30 does not have to transfer any current, but only potentials, in order to control the re eater properly.

The invention 1s not limited to the details of the disclosure, but is capable of variousand widely different embodiments within the spirit and scope of the appended claims.

The invention claimed 1s:

1. A transmission system and two oppositely ointed asymmetrically transmitting channe s connected thereto, and means responsive to the transmission in said system for decreasing the transmitting efficiency of one of said channels and for maintaining one of said channels at low transmitting efiiciency at the instant when transmission is initially incident upon said channels, said means comprising circuits? for balancing the energy of the transmission at one part of the system against the energy of the transmission at another part of the system.

2. A transmission system comprising a line and two oppositely pointed asymmetrically transmitting channels connected thereto, and means responsive to'the transmission in said system for controlling the transmit- A ting efliciency of said channels, said means comprising a control element stable in each of two different conditions of operation and unstable inintermediate conditions, for cansin one ,of said channels to have higher ef ciency than the other in one of said conditions of stability and causing said other channel to have hi her transmitting efliciency than said one c annel in, said other condition of stability, and said means also com- L prising circuits for balancing the energy of the transmission at one part of the system against the energy of the transmission at another part of the s stem and controlling the operation of said e ement in accordance with the resultant energy.

3. A transmitting system comprising two two-way transmitting line sections connected by two .oppositely pointed. asymmetrically transmitting channels, a control element,

stable in 'each of two difierent conditions and unstable in intermediate conditions, for

. causing one of said channels to have a transmitting efficiency higher than that of the other 1110116 of said conditions of stability and causing said other channel to have the higher transmission efiiciency in said other condition of stability, and two circuits, both connected to said control element and one connected to one of said line sections and the other connected to said other line section, selectively responsive to opposite directions of alternating current energy flow in said line to cause said control element to have one or the other of said conditions of stability according to the direction of flow of alternating current'energy in said line.

. efficient for transmission.

4. The method of operating a two-way two channel repeater in a'line, which comprises maintaining one'of said channels at relatively low' transmitting etficiency and the other at relatively high transmittin cfficiency during the instant when signa s of the direction last transmitted over the line are initially incident u on the repeater, and

maintaining said hig ly eflicient channel highly efficient continuously until a cessation of signals approaching "the repeater.

5. The method of operating a two-way transmitting circuit, an asymetrically transmitting signaling channel for transmitting signals to said circuit and-a separate asymmetrically transmitting signaling channel for transmitting signals 'from said 'cir-- transmitti g efiiciency, continuously whenever neither channel is transmitting.

7. The method of o crating a signal transmitting station inc uding two signal repeating devices pointed in opposite directions in a transmission system, which comprises maintainin the -repeater which last transmitted at refiitively .high transmitting eificiency and the other at relatively low transmitting efiiciency continuously whenever neither re eater 1s transmitting.

8. The method of operating a signal transmitting station including two asymmetrically transmitting space is charge signal repeating devices pointed in opposite d1- rections in a transmission system, which comprises continuously, whenever neither device is transmitting, maintaining for the device which last transmitted the signals a field of force of such value as to permit said device to transmit relatively efficiently, and at the same. time maintaining for the other device a field of force competent to maintain the last mentioned device relatively in- 9. A two-way signal transmitting s stem comprising separate" signaling channe s for transmitting signals in each direction, a space discharge device in each channel and functioning as .an essential element for maintaining eflicient transmission therethrough, an electrode in each of said devices,

y transmitting chan-,

and means for automatically, continuously when neither device is transmitting, mainsaid electrode of said other device at such a potential as to maintain the last mentioned device relatively ineflicient for transmission.

10. The method of operating an asymmetrically transmitting space discharge signal transmitting device in a signaling line which comprises, after each cessation of transmission of signals through said device, maintaining said device at relatively high transmitting efliciency until reversal of the direction of approach toward said device of signals to be transmitted through said line, and thereupon rendering said device relatively inefiicient t transmit, while main- };aining the connections of the device to the 11. A system comprising a line, repeating means associated therewith, and means for automatically reversing the operative direction of said repeating means with respect to said line Without changing, its circuital state of continuity with respect to said line, and maintaining said reversed operative direction of the repeating means, aftereach cessation of transmission, until reversal of the direction of approach toward said repeating means of impulses to be repeated.

12. A two-way transmitting circuit, an asymmetrically transmitting channel for transmitting to said circuit, an asymmetrically transmitting channel for transmitting from said circuit, and means effective, in response to substantially merely initial incidence of the transmission upon one of said channels, to cause one of said channels to have for a time of the order of seconds a transmitting efliciency high relatively to that which ithad before said incidence, while permitting the circuit arrangement of said channels and said line to remain unaltered.

13. The method of repeating in a line.

transmitting channel for transmitting signals to said circuits and an asymmetrically transmitting channel for transmitting Slgnals from said circuit, which comprlses, after each cessation of transmission through said circuit, maintaining the signal channel repeating which last transmitted at a relatively high transmitting efliciency and the other signal channel at a relatively low transmitting efliciency until reversal of the direction of ap-- proach toward said channels of the signals to be transmitted through said circuit, and thereupon rendering the highly eflicient transmitting channel relatively ineificient for transmitting and the other channel relatively efiicient for transmitting, while maintaining the circuit arrangement of said channels and said line unaltered.

15. A signal transmitting system comprising a plurality of circuits having a fixed state of continuity and including a two-way transmitting circuit, an asymmetrically transmitting channel for transmitting signals to said circuit, and an asymmetrically transmitting channel for transmitting signals from said circuit, said system also comprising means for automatically, after each cessation of transmission through said circuit, maintaining the signal channelwhich last transmitted at a relatively high transmitting efiiciency and the other signal channel at a relatively low transmitting efiiciency until reversal of the direction of a proach toward said channels of the signa s to be transmitted through said system, and thereupon renderin the highly eflicient channel relatively ine cient and the other channel relatively eificient for transmitting.

16. In signaling apparatus, a station comfor supplying space current to said tubes,

and means for automatically maintaining the direct space current in one of said tubes at zero value and in one at normal operating value, substantiall all of the time the station is in condition or use, and maintaining the particular tube which happens to have its space current at normal value at any instantcontinuously operative until current approaches its output over said circuit.

17. In signaling apparatus, a station comprising a two-way signal transmitting circuit, an asymmetrically transmitting channel pointed in one direction for transmitting signals to said circuit, an asymmetrically transmitting channel oppesitely pointed with respect to said circuit for transmitting signals from saidcircuit, a. relay for controlling the transmitting efiiciency of one of said channels relatively to that of the other, said relay being stable under two difierent conditions of o eration and unstable in intermediate con itions, and means responsive to the transmission in said channels for causing operation of said relay from one of said conditions of stability to the other.

18. A repeating system comprising two three-electrode electron tube repeaters in" separate paths, the output side of each path being connected to the input side of the other, a three-electrode electron tube associated with the input of one of said repeaters, a second three-electrode electron tube associated with the input of the other repeater, a third electron tube associated with the output of said one repeater, a fourth electron tube associated with the output of said other repeater, animpedance difierentially connected in the output circuits of said first and third electron tubes, and impedance differentially connected in the output circuits of said second and fourth electron tubes, said four electron tubes being adjusted to have zero output current for zero mfimt and their gains being so adjusted that w enever an input electron tube and an ouput electron tube associated with a repeater are both delivering current to one of said impedances the current delivered by the input tube is greater than the current delivered by the output tube, and a vacuum tube relay having its input in circuit with said impedances and having its output connected to supply potentials of one sign to control electrodes of one of said repeaters and its input tube and connected to supply potentials of the o posite sign to control electrodes of the ot er repeater and itemput tube, said relay bein stable under two difi'erent conditions of vo ta e input thereto and unstable under interme iate conditions, and bein operable from one of said conditions to t e other by the application thereto of an input voltage derived from'said impedances.

19. The method of operating a two-way two-channel electron tube repeater in a circuit which comprises, substantially all of the time the repeater is in condition for use, maintaining the direct space current of a tube in one of said channels at zero value and of a tube in the other channel at a value corresponding to a distortionless amplification point on the grid potential-plate current characteristic of the tube, and always maintaining the particular tube which happens to have its space current at said point on the tube characteristic at any instant continuously operative until transmission in the system starts or ceases.

20. The method of operating repeating system including a line and arepeater therein having two electron tube signal'repeating paths the output of each of which is con nected to the input of the other, which comprises maintaimng one of said paths at relatively low transmitting efliclency during the instantwhen signals to be repeated are initially incident upon the repeater. and ma1ntainin on the grid of the repeating tube in the ot er path, during said instant, a; pure direct current control potential, as. distin- 1 ,eemaa guished from the signaling potential, of such value and sign as to render said last mentioned tube relatively elficient for transmitting.

21. The method of operating a repeating system includin a line and a repeater therein having two e ectron tube slgnal repeating paths the output of each of which is connected .to the input of the other, which comprises maintainmg one of said paths at relatively low transmitting efliciency during the instant when signals to be repeated are initially incident upon therepeater and, from said instant until the cessationof si als approaching the repeater; continuous y maintaining a pure'direct current control potential on the grid of the tube in said other path of such value and sign that'th'e last mentioned tube is relatively eflicient for ing pointed in the same direction around said triangle, saidtwo amplifiers having their input circuits. at one apex of the triangle, said. unilateral 'device having its input connected to said line and to the output of said one am lifier, and said other amplifier and saicii unilateral device having their out ut circuits connected together, and in opposition, to said control element.

,23. A transmission system and two oppo- I sitely pointed asymmetrically transmitting channels connected thereto, and means responsive to the transmission in said system for decreasing the transmitting efliciency of one of said channels and for maintaining one of said channels at low transmitting ef- 'ficiency at the instant when transmissionfiis initially incident upon said channels, sald means comprising circuits for balancing the energy of the transmission at one part of the system against the energy of the transmission at another part of the system, and said means operating in response. to the difference of said energies.-

24. In a signaling system, a station comprising a twoway signal transmitting cir-' cu t, an asymmetrically transmitting'channel for transmitting signals to said circuit,

an asymmetrically transmitting channel for transmitting signals from said circuit, and

means for automatically maintaining the channel which last trans'mittedat relatively high transmitting efliciency, and the other in response to the difference of said enermes. b

In witness whereof, I hereunto subscribe 10 I my namethis 12th day of January, A. D. 1923.

WILLIAM S. GORTON. 

